RFID for location of the load on a tower crane

ABSTRACT

A radio frequency identification (RFID) tower crane load locator and sway indicator is disclosed and includes: a plurality of RFID tags at different locations on or around the tower crane; at least two RFID readers at different locations on the tower crane; a navigation satellite system (NSS) position receiver; and a load information interface. The RFID readers comprising a range determiner to provide range measurements between each of the RFID readers and each of the plurality of RFID tags. The sway determiner is coupled with a hook block of the tower crane. The NSS position receiver is coupled with the tower crane. The load information interface to combine information from range measurements, the sway determiner and the NSS position receiver to generate location and sway information of the load with respect to the tower crane and provide the location and sway information in a user accessible format.

CROSS-REFERENCE TO RELATED APPLICATIONS—DIVISIONAL

This application is a divisional application of and claims the benefitof co-pending U.S. patent application Ser. No. 13/324,605 filed on Dec.13, 2011 entitled “RFID FOR LOCATION OF THE LOAD ON A TOWER CRANE” byJohn F. Cameron et al., and assigned to the assignee of the presentapplication; the disclosure of U.S. patent application Ser. No.13/324,605 is hereby incorporated herein by reference in its entirety.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending U.S. patent application Ser.No. 14/247,132 filed on Apr. 7, 2014, entitled “RFID FOR LOCATION OF THELOAD ON A TOWER CRANE,” by John F. Cameron et al., and assigned to theassignee of the present application.

BACKGROUND

Tower cranes are used in many different applications. For example, onconstruction sites, tower cranes are used to move large and/or heavyobjects from one location to another.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthis application, illustrate and serve to explain the principles ofembodiments in conjunction with the description. Unless noted, thedrawings referred to this description should be understood as not beingdrawn to scale.

FIG. 1A is an illustration of an RFID tower crane load locator systemutilizing a single RFID reader for determining the location of a loadaccording to one embodiment of the present technology.

FIG. 1B is an illustration of an RFID tower crane load locator systemutilizing two RFID readers for determining the location of a loadaccording to one embodiment of the present technology.

FIG. 1C is an illustration of an RFID tower crane load locator systemutilizing three RFID readers for determining the location of a loadaccording to one embodiment of the present technology.

FIG. 2 is a block diagram of an RFID tower crane load locator system,according to one embodiment of the present technology.

FIG. 3 is a flowchart of a method for utilizing RFID for locating theload of a tower crane, according to one embodiment of the presenttechnology.

FIG. 4 is a flowchart of a method for utilizing RFID for locating theload of a tower crane, according to one embodiment of the presenttechnology.

FIG. 5 is a block diagram of an example computer system upon whichembodiments of the present technology may be implemented.

FIG. 6 is a block diagram of an example global navigation satellitesystem (GNSS) receiver which may be used in accordance with oneembodiment of the present technology.

DESCRIPTION OF EMBODIMENT(S)

Reference will now be made in detail to various embodiments of thepresent technology, examples of which are illustrated in theaccompanying drawings. While the present technology will be described inconjunction with these embodiments, it will be understood that they arenot intended to limit the present technology to these embodiments. Onthe contrary, the present technology is intended to cover alternatives,modifications and equivalents, which may be included within the spiritand scope of the present technology as defined by the appended claims.Furthermore, in the following description of the present technology,numerous specific details are set forth in order to provide a thoroughunderstanding of the present technology. In other instances, well-knownmethods, procedures, components, and circuits have not been described indetail as not to unnecessarily obscure aspects of the presenttechnology.

Unless specifically stated otherwise as apparent from the followingdiscussions, it is appreciated that throughout the present descriptionof embodiments, discussions utilizing terms such as “receiving”,“storing”, “generating”, “transmitting”, “inferring,” or the like, referto the actions and processes of a computer system, or similar electroniccomputing device. The computer system or similar electronic computingdevice manipulates and transforms data represented as physical(electronic) quantities within the computer system's registers andmemories into other data similarly represented as physical quantitieswithin the computer system memories or registers or other suchinformation storage, transmission, or display devices. Embodiments ofthe present technology are also well suited to the use of other computersystems such as, for example, mobile communication devices.

Overview

Embodiments of the present invention enable the determination of thelocation of a load of a tower crane. In the following discussion, theload location is the actual or physical location of the load. In oneembodiment, the load location is defined with respect to the relationallocation of a portion of the tower crane, such as, but not limited to,the base, mast, cab and the like. In addition, the load locationinformation is provided at a user interface in a user accessible format,such as, for example on a graphical user interface.

By providing load location information at a user interface, embodimentsof the present technology enable safer and more efficient operation of atower crane, which results in lower operating cost and improved safety.For example, the load location information can be displayed to the towercrane operator thereby allowing the operator to accurately monitor andcontrol the load location. Moreover, the information can also bedisseminated to other users including project managers, foremen and thelike. In so doing, additional layers of operational insight and towercrane safety are achieved.

With reference now to FIG. 1A, an illustration of a tower crane 100including an RFID tower crane load locator system for determining thelocation of a load is shown. In general, RFID may refer to a number ofdifferent RFID transmission methods including, but not limited to, lowfrequency (LF), high frequency (HF), ultra high frequency (UHF) andultra wide band (UWB).

Tower crane 100 includes a base 104, a mast 102 and a jib (e.g., workingarm) 110. The mast 102 may be fixed to the base 104 or may be rotatableabout base 104. The base 104 may be bolted to a concrete pad thatsupports the crane or may be mounted to a moveable platform. In oneembodiment, the operator 130 is located in a cab 106 which includes auser interface 137.

Tower crane 100 also includes a trolley 114 which is moveable back andforth on jib 110 between the cab 106 and the end of the jib 110. A cable116 couples a hook 122 and hook block 120 to trolley 114. Acounterweight 108 is on the opposite side of the jib 110 as the trolley114 to balance the weight of the crane components and the object beinglifted, referred to hereinafter as load 118.

In one embodiment shown in FIG. 1A, tower crane 100 also includes anRFID reader 126 and a number of RFID tags 124. In one embodiment RFIDreader 126 is battery powered and may include rechargeablecharacteristics including solar charging capabilities. In anotherembodiment, RFID reader 126 is electrically wired with tower crane 180.

In FIG. 1A, the RFID reader 126 is shown on trolley 114 and RFID tags124 are located at hook block 120, cab 106 and load 118. However, inother embodiments RFID reader 126 may be located at a different locationand the RFID tags 124 would be adjusted accordingly. For example, ifRFID reader 126 was located on hook block 120 then RFID tags 124 couldbe located at trolley 114 and cab 106. In another example, if RFIDreader 126 was located at cab 106 then RFID tags 124 could be located attrolley 114 and hook block 120. In yet another embodiment, there may benumerous RFID tags 124 located at different locations both on and off oftower crane 100, such as for example on load 118.

Tower crane 100 also includes a jib direction determiner 128. Ingeneral, jib direction determiner 128 determines the direction that jib110 is facing. In various embodiments, jib direction determiner 128 maybe a compass, a heading indicator, a satellite navigation positionreceiver offset from a known position, a satellite navigation positionreceiver utilizing two antenna located at different points along thejib, at least two satellite navigation position devices located atdifferent points along the jib or a combination thereof. In oneembodiment, such as shown in FIG. 1C, no jib direction determiner isutilized.

FIG. 1A additionally includes a sway determiner 133 coupled with hookblock 120. In one embodiment, sway determiner 133 may be anaccelerometer, a gyro, GNSS, a camera and the like. In general, swaydeterminer 133 is used to determine sway of the load 118. Although swaydeterminer 133 is shown as coupled with hook block 120, in anotherembodiment, the sway determiner 133 may be coupled with the load 118 orthe hook 122.

Referring now to FIG. 1B, an illustration of a tower crane 145 includingan RFID tower crane load locator system utilizing two RFID readers fordetermining the location of a load is shown.

For purposes of clarity in the discussion, the description of some ofthe components of FIG. 1B that are similar to and previously describedin FIG. 1A are not repeated herein.

In one embodiment, in addition to the components described in FIG. 1A,FIG. 1B includes a second RFID reader 126 located at a differentlocation than the first RFID reader 126. In addition, since a number ofRFID reader's 126 are utilized, one or more components may have both anRFID reader 126 and an RFID tag 124 coupled therewith. In anotherembodiment, RFID reader 126 may include an RFID tag 124.

For example, in FIG. 1B, a first RFID reader 126 with an RFID tag 124 islocated at trolley 114. The second RFID reader 126 with an RFID tag 124is located at cab 106. Although the two locations are shown, thetechnology is well suited for locating RFID readers 126 at various otherlocations, such as, but not limited to, hook block 120, load 118, mast102, jib 110 and the like.

Range measurement paths 187, 188 and 189 are also shown in FIG. 1B. Ingeneral, range measurement paths illustrate a pulse sent from an RFIDreader 126 and returned from the RFID tag 124. As described in moredetail herein, these range measurements are used to determine distances.

FIG. 1B also includes GNSS devices 140. In general, GNSS device 140 maybe a complete GNSS receiver or just a GNSS antenna. In one embodiment,there are two GNSS devices 140. One is located at the front of the jib110 and the other is located at counterweight 108. Although two GNSSdevices 140 are shown, in another embodiment, FIG. 1B may only utilizesone GNSS device 140. For example, one GNSS device 140 may provide alocation while jib direction determiner 128 determines the directionthat jib 110 is facing. In yet another embodiment jib directiondeterminer 128 may be a GNSS receiver utilizing two GNSS antenna locatedat different points along the jib such as those designated by GNSSdevices 140. In addition, the locations of GNSS devices 140 may be indifferent areas, the illustration of the two GNSS devices 140 locationsin FIG. 2B is provided merely for purposes of clarity.

Referring now to FIG. 1C, an illustration of a tower crane 166 includingan RFID tower crane load locator system utilizing at least four RFIDcomponents 125 to provide RFID range measurements between the at leastfour RFID components 125.

For purposes of clarity in the discussion, the description of some ofthe components of FIG. 1C that are similar to and previously describedin FIGS. 1A and 1B are not repeated herein.

In one embodiment, FIG. 1C includes at least four RFID components 125.In one embodiment, the at least four RFID components include at leastthree RFID readers 126 and at least one RFID tag 124. In one embodiment,at least one of the RFID components 124 is not in the same plane as themast 102 and the jib 110 of the tower crane. For example, in oneembodiment, at least one of the four RFID components 125 is locatedseparately from the tower crane 166. In the example shown in FIG. 1C,the off-tower RFID component 125 is a handheld device. In one embodimentthe off-tower RFID component 125 is carried by a user 131. As will bedescribed in more detail herein, the user may be a foreman, safetyinspector, or the like. In another embodiment, user 131 may be the towercrane operator and as such operator 130 would not need to be in the cab106.

In general, since at least four RFID components 125 are utilized, it ispossible to utilize the RFID range measurements independent of any otheraspects of the crane to determine a location of load 118. For example,by utilizing four RFID components 125 without the jib determiner 128 orsway determiner 133, the RFID load locator would provide informationregarding the location of the load 118. In addition, since the four RFIDcomponents do not require additional input from the crane or craneoperator to provide load location information, in one embodiment, thecomponents can be provided as a stand-alone load locating device thatcan be added to an existing tower crane without requiring anymodification or manipulation of existing crane components.

With reference now to FIG. 2, a tower crane RFID load locator 200 isshown in accordance with an embodiment of the present technology. In oneembodiment, RFID load locator 200 includes an RFID range measurer 210, aload position determiner 230 and a load information generator 240. Inone embodiment, RFID load locator 200 may also include a jib directiondeterminer 128. However, in another embodiment, RFID load locator 200may optionally receive jib direction determiner 128 information from anoutside source. Similarly, RFID load locator 200 may optionally receivesway determiner 133 information from an outside source.

In one embodiment, RFID range measurer 210 provides RFID rangemeasurements between at least four RFID components 125. Load positiondeterminer 230 utilizes the range measurements with or without any otheroptional inputs described herein to determine a location of the load118. Load information generator 240 provides the location of the loadinformation suitable for subsequent access by a user. In one embodiment,the location of the load information is output in a user accessibleformat 250. For example, the load information may be output to a graphicuser interface (GUI), such as GUI 137. In another embodiment, the loadinformation provided in user accessible format 250 may be sent to oraccessed by a plurality of devices such as a handheld device, GUI 137,or other devices. In another embodiment, the RFID range measurer may beat a tower crane in a first location and the range measurements may beprovided to a load position determiner 230 at a remote location. In yetanother embodiment, the load information generator 240 may also beremotely located or may be remotely accessible by authorized personnel.For example, the load location information may be processed in a localoffice at the work site, remote from the work site or the like and theload information generator 240 may be stored in “the cloud”.

Optional Jib direction determiner 128 determines the direction the jibis facing. Optional sway determiner 133 is used to determine sway of theload 118. Although sway determiner 133 is shown as coupled with hookblock 120, in another embodiment, the sway determiner 133 may be coupledwith the load 118 or the hook 122.

In one embodiment, in addition to utilizing the range measurements todetermine a location of the load, load position determiner 230 may alsoutilize the optional jib direction information or the sway determiner133 information or both the jib direction information and the swaydeterminer 133 information to determine the location of the load 118.

FIG. 3 is a flowchart of a method for utilizing RFID for locating theload of a tower crane, according to one embodiment of the presenttechnology.

With reference now to 302 of FIG. 3 and FIG. 1A, one embodimentgenerates range measurements from an RFID reader coupled with the towercrane to at least a first and a second RFID tag coupled with the towercrane.

In other words, RFID reader 126 can be used in conjunction with RFIDtags 124 to determine distances. For example, RFID reader 126 wouldmeasure the range to the RFID tag 124 located on hook block 120. In sodoing, the distance 188 between hook block 120 and trolley 114 can bedetermined.

Similarly, RFID reader 126 can measure the range to the RFID tag 124located on cab 106. In so doing, the distance of leg 189 between cab 106and trolley 114 can be determined.

In another embodiment, such as shown in FIG. 1B where RFID reader 126 islocated at hook block 120 or cab 106, similar measurements can be madebetween the RFID tags and once two sides of the triangular plane areknown, the third side can be calculated. For example, assuming the RFIDreader 126 was located at cab 106; leg 189: the distance between cab 106and trolley 114 could be measured. Similarly leg 187: the distancebetween cab 106 and hook block 120 could also be measured. Then,distance 188 could be solved for using a formula such as the PythagoreanTheorem.

With reference now to 304 of FIG. 3 and FIG. 1A, one embodimentdetermines a jib direction. As stated herein, the jib direction may bedetermined by numerous devices including, but not limited to, a compass,a laser direction finder, one or more GNSS receivers, or the like. Inanother embodiment, the jib direction may be determined by otherelements associated with GNSS including: Differential GPS, Real-timeKinematic (RTK), and Network RTK systems. Each of these systems isdescribed in further detail in the description of FIG. 6.

With reference now to 306 of FIG. 3 and FIG. 1A, one embodiment combinesthe range measurements and the jib direction to generate a location ofthe load. For example, in one embodiment the range measurements willprovide a location of the load as a given distance 189 and height 188from the cab 106. However, the information is not directional but woulddefine a radius of an arc or a circle. By incorporating the jibdirection, a specific location on the arc or circle would be defined.

With reference now to 308 of FIG. 3 and FIG. 1A, one embodiment providesthe information on a user interface in a user accessible format. Thatis, the information may be presented on a user interface, such as agraphical user interface (GUI) or the like. In addition, the informationmay be presented as an overlay on a map such as a site map or the like.

For example, a site map is used to organize and monitor activities on aconstruction site. The site map may indicate the location (or range oflocations) where contact between the tower crane and another object ispossible. It is important for the tower crane to not enter a restrictedspace where an accident could occur. Thus, in addition to providinginformation to be presented on the user interface, one embodiment mayalso provide warning information. In another embodiment, an automatedstop or override may also be utilized.

For example, the load location information can be used to alertoperators when they are not moving safely in terms of location, speed,acceleration, shock, load, jerk, etc. The information can also be usedto automatically keep the tower crane within a predefined motion orpath.

FIG. 4 is a flowchart of a method for utilizing RFID for locating theload of a tower crane, according to one embodiment of the presenttechnology.

With reference now to 402 of FIG. 4 and FIGS. 1B and 1C, one embodimentgenerates range measurements from a plurality of RFID readers to aplurality of RFID tags coupled with the tower crane. For example, inFIG. 1B, a first RFID reader 126 with an RFID tag 124 is located attrolley 114. The second RFID reader 126 with an RFID tag 124 is locatedat cab 106. Although the two locations are shown, the technology is wellsuited for locating RFID readers 126 at various other locations, suchas, but not limited to, hook block 120, load 118, mast 102, jib 110 andthe like.

In addition, since a number of RFID reader's 126 are utilized, one ormore components may have both an RFID reader 126 and an RFID tag 124coupled therewith. In another embodiment, RFID reader 126 may include anRFID tag 124.

As described herein, these range measurements are used to determinedistances.

In one embodiment, a third RFID reader 126 may be located separatelyfrom the tower crane 166. As shown in FIG. 1C, the third RFID reader 126may be a handheld device. Since three RFID reader's 126 are utilized, itis possible to utilize the range measurements to determine a load 118location that is outside of a plane. For example, the third RFID reader126 would provide information that could be utilized to determine a swayof load 118.

Moreover, in one embodiment the third RFID reader 126 is carried by auser 131. User 131 may be a foreman, safety inspector, manager, owner,developer, or the like. In another embodiment, user 131 may be the towercrane operator and as such operator 130 would not need to be in the cab106.

With reference now to 304 of FIG. 4 and FIGS. 1B and 1C, one embodimentdetermines a jib direction. In one embodiment, one or more GNSS devices140 coupled with the tower crane are utilized to determine the jibdirection.

In general, GNSS device 140 may be a complete GNSS receiver or just aGNSS antenna. In one embodiment, there are two GNSS devices 140. One islocated at the front of the jib 110 and the other is located atcounterweight 108. Although two GNSS devices 140 are shown, in anotherembodiment, only one GNSS device 140 may be utilized. For example, oneGNSS device 140 may provide a location while jib direction determiner128 determines the direction that jib 110 is facing. In yet anotherembodiment jib direction may be determined by a GNSS receiver utilizingtwo GNSS antenna located at different points along the jib such as thosedesignated by GNSS devices 140 at FIG. 1C. In another embodiment, thelocations of GNSS devices 140 may be in different locations on the towercrane.

With reference now to 405 of FIG. 4 and FIG. 1B, one embodiment fixedlycouples a sway determiner 133 with a hook block of the tower crane, thesway determiner 133 to provide sway information with respect to the hookblock 120. Although sway determiner 133 is stated as being coupled withhook block 120, in another embodiment, the sway determiner 133 may becoupled with the load 118 or the hook 122.

With reference now to 406 of FIG. 4 and FIG. 1B, one embodiment combinesthe range measurements, the jib direction and the sway determinerinformation to generate a location of the load. For example, by usingtwo RFID readers 126 in a similar manner as described in 302 of FIG. 3,a plurality of distance measurements for legs 187, 188 and 189 can bedetermined.

However, when the second RFID reader 126 is located at hook block 120 orcab 106, while the measurements can be made between the RFID tags andonce two sides of the triangular plane, the sway determiner informationcan be added to further refine the third side calculation. For example,assuming one of the RFID readers 126 was located at cab 106, legs 187and 189 could be measured. By including the sway determiner 133information, solving for the length of leg 188 can now be performed by amore accurate method such as the Law of Cosines, where the swaydeterminer information is used to determine the cosine for the angle.

In another embodiment, such as shown in FIG. 1C, three RFID readers canbe used to make range measurements and utilize the measurements toprovide a position fix utilizing methods such as “trilateration.” Forexample, to solve for the load 118 position information, the informationfrom RFID readers 126 located at the trolley 114, the cab 106 and thehand-held device held by user 131 is used to formulate the equationssuch as for three spherical surfaces and then solving the threeequations for the three unknowns, x, y, and z. This solution can then beutilized in a Cartesian coordinate system to provide three-dimensionalinformation.

Range measurements can be made, in one embodiment, by counting the timeinterval from time of transmission of a pulse to a reader to its returnto the reader from the tag, and dividing by 2. So for a round-tripelapsed time interval of 60 nanoseconds, the true one-way time of flightis 30 nanoseconds, which corresponds to 30 feet. Such elapsed timemeasurements involve the use of a precision clock with start-stoptrigger capabilities. In one embodiment, the RFID reader is equippedwith this type of range measurer. Other methods for making rangemeasurements include estimating distance include signal strength (RSSI),“instantaneous phase” which is similar to real-time-kinematic (RTK) GPSmethods, and integrated phase which continuously tracks phase as if itwere a tape measure.

In one embodiment, the additional jib direction information, the swaydeterminer information, or both can also be added to the trilaterationinformation to generate additional useful information regarding loadlocation, motion, rotation, and the like.

With reference now to 308 of FIG. 4 and FIGS. 1B and 1C, one embodimentprovides the information on a user interface in a user accessibleformat. That is, the information may be presented on a user interface,such as a graphical user interface (GUI) or the like. For example, theinformation may be a presented as plan and/or elevation views of thetower crane with the location of the load illustrated spatially withrelation to an illustration of the tower crane. In addition, theinformation may be presented as an overlay on a map such as a site mapor the like.

For example, the site map may indicate the location (or range oflocations) where contact between the tower crane and another object ispossible. Thus, in addition to providing information to be presented onthe user interface, one embodiment may also provide warning information.In another embodiment, an automated stop or override may also beutilized.

For example, the load location information can be used to alertoperators when they are not moving safely in terms of location, speed,acceleration, shock, load, jerk, etc. The information can also be usedin automatic collision avoidance.

Collision Avoidance

For example, the load 118 location can be compared to the location ofother devices and/or other objects. Moreover, if a safety zone isbreached, e.g., an area a prescribed distance from the other device orobject, a warning can be generated about the potential collision. In oneembodiment, a safety threshold distance is used to help preventcollisions.

In another embodiment, the load location can be compared to pre-defined“do not enter” spaces. In this embodiment, pre-planning establishesareas or zones that should not be entered by particular devices. When itis determined that a load 118 has entered, or is about to enter, a “donot enter” zone, a warning can be generated and provided to theoperator. The warning can help prevent collisions between the towercrane and other objects.

In yet another embodiment, in addition to providing a warning, theoperation of the tower crane may be automatically stopped or otherwisemanipulated to stop a collision or boundary incursion from actuallyoccurring. For example, the system may include a first warning distancefrom an object or area having a first radius and also a second automaticoverride distance from an object or area at a smaller radius.

As such, if a load was approaching another object, as the warningdistance is breached, the system would provide a user warning. However,if the load breached the automatic override distance, the operation ofthe tower crane may be automatically stopped, reversed, or the like. Inso doing, significant safety risks and property damage may beautomatically avoided.

It is appreciated that the autonomous position of the tower crane can beused to generate a real-time graphical representation of a work site. Inone embodiment, the autonomous position of the tower crane is reportedto a remote location where the activity can be monitored.

Computer System

With reference now to FIG. 5, portions of the technology for providing acommunication composed of computer-readable and computer-executableinstructions that reside, for example, in non-transitory computer-usablestorage media of a computer system. That is, FIG. 5 illustrates oneexample of a type of computer that can be used to implement embodimentsof the present technology. FIG. 5 represents a system or components thatmay be used in conjunction with aspects of the present technology. Inone embodiment, some or all of the components of FIG. 1 or FIG. 3 may becombined with some or all of the components of FIG. 5 to practice thepresent technology.

FIG. 5 illustrates an example computer system 500 used in accordancewith embodiments of the present technology. It is appreciated thatsystem 500 of FIG. 5 is an example only and that the present technologycan operate on or within a number of different computer systemsincluding general purpose networked computer systems, embedded computersystems, routers, switches, server devices, user devices, variousintermediate devices/artifacts, stand-alone computer systems, mobilephones, personal data assistants, televisions and the like. As shown inFIG. 5, computer system 500 of FIG. 5 is well adapted to havingperipheral computer readable media 502 such as, for example, a floppydisk, a compact disc, and the like coupled thereto.

System 500 of FIG. 5 includes an address/data bus 504 for communicatinginformation, and a processor 506A coupled to bus 504 for processinginformation and instructions. As depicted in FIG. 5, system 500 is alsowell suited to a multi-processor environment in which a plurality ofprocessors 506A, 506B, and 506C are present. Conversely, system 500 isalso well suited to having a single processor such as, for example,processor 506A. Processors 506A, 506B, and 506C may be any of varioustypes of microprocessors. System 500 also includes data storage featuressuch as a computer usable volatile memory 508, e.g. random access memory(RAM), coupled to bus 504 for storing information and instructions forprocessors 506A, 506B, and 506C.

System 500 also includes computer usable non-volatile memory 510, e.g.read only memory (ROM), coupled to bus 504 for storing staticinformation and instructions for processors 506A, 506B, and 506C. Alsopresent in system 500 is a data storage unit 512 (e.g., a magnetic oroptical disk and disk drive) coupled to bus 504 for storing informationand instructions. System 500 also includes an optional alpha-numericinput device 514 including alphanumeric and function keys coupled to bus504 for communicating information and command selections to processor506A or processors 506A, 506B, and 506C. System 500 also includes anoptional cursor control device 516 coupled to bus 504 for communicatinguser input information and command selections to processor 506A orprocessors 506A, 506B, and 506C. System 500 of the present embodimentalso includes an optional display device 518 coupled to bus 504 fordisplaying information.

Referring still to FIG. 5, optional display device 518 of FIG. 5 may bea liquid crystal device, cathode ray tube, plasma display device orother display device suitable for creating graphic images andalpha-numeric characters recognizable to a user. Optional cursor controldevice 516 allows the computer user to dynamically signal the movementof a visible symbol (cursor) on a display screen of display device 518.Many implementations of cursor control device 516 are known in the artincluding a trackball, mouse, touch pad, joystick or special keys onalpha-numeric input device 514 capable of signaling movement of a givendirection or manner of displacement. Alternatively, it will beappreciated that a cursor can be directed and/or activated via inputfrom alpha-numeric input device 514 using special keys and key sequencecommands.

System 500 is also well suited to having a cursor directed by othermeans such as, for example, voice commands. System 500 also includes anI/O device 520 for coupling system 500 with external entities. Forexample, in one embodiment, I/O device 520 is a modem for enabling wiredor wireless communications between system 500 and an external networksuch as, but not limited to, the Internet. A more detailed discussion ofthe present technology is found below.

Referring still to FIG. 5, various other components are depicted forsystem 500. Specifically, when present, an operating system 522,applications 524, modules 526, and data 528 are shown as typicallyresiding in one or some combination of computer usable volatile memory508, e.g. random access memory (RAM), and data storage unit 512.However, it is appreciated that in some embodiments, operating system522 may be stored in other locations such as on a network or on a flashdrive; and that further, operating system 522 may be accessed from aremote location via, for example, a coupling to the internet. In oneembodiment, the present technology, for example, is stored as anapplication 524 or module 526 in memory locations within RAM 508 andmemory areas within data storage unit 512. The present technology may beapplied to one or more elements of described system 500. For example, amethod of modifying user interface 225A of device 115A may be applied tooperating system 522, applications 524, modules 526, and/or data 528.

System 500 also includes one or more signal generating and receivingdevice(s) 530 coupled with bus 504 for enabling system 500 to interfacewith other electronic devices and computer systems. Signal generatingand receiving device(s) 530 of the present embodiment may include wiredserial adaptors, modems, and network adaptors, wireless modems, andwireless network adaptors, and other such communication technology. Thesignal generating and receiving device(s) 530 may work in conjunctionwith one or more communication interface(s) 532 for coupling informationto and/or from system 500. Communication interface 532 may include aserial port, parallel port, Universal Serial Bus (USB), Ethernet port,antenna, or other input/output interface. Communication interface 532may physically, electrically, optically, or wirelessly (e.g. via radiofrequency) couple system 500 with another device, such as a cellulartelephone, radio, or computer system.

The computing system 500 is only one example of a suitable computingenvironment and is not intended to suggest any limitation as to thescope of use or functionality of the present technology. Neither shouldthe computing environment 500 be interpreted as having any dependency orrequirement relating to any one or combination of components illustratedin the example computing system 500.

The present technology may be described in the general context ofcomputer-executable instructions, such as program modules, beingexecuted by a computer. Generally, program modules include routines,programs, objects, components, data structures, etc., that performparticular tasks or implement particular abstract data types. Thepresent technology may also be practiced in distributed computingenvironments where tasks are performed by remote processing devices thatare linked through a communications network. In a distributed computingenvironment, program modules may be located in both local and remotecomputer-storage media including memory-storage devices.

GNSS Receiver

With reference now to FIG. 6, a block diagram is shown of an embodimentof an example GNSS receiver which may be used in accordance with variousembodiments described herein. In particular, FIG. 6 illustrates a blockdiagram of a GNSS receiver in the form of a general purpose GPS receiver680 capable of demodulation of the L1 and/or L2 signal(s) received fromone or more GPS satellites. For the purposes of the followingdiscussion, the demodulation of L1 and/or L2 signals is discussed. It isnoted that demodulation of the L2 signal(s) is typically performed by“high precision” GNSS receivers such as those used in the military andsome civilian applications. Typically, the “consumer” grade GNSSreceivers do not access the L2 signal(s). Further, although L1 and L2signals are described, they should not be construed as a limitation tothe signal type; instead, the use of the L1 and L2 signal(s) is providedmerely for clarity in the present discussion.

Although an embodiment of a GNSS receiver and operation with respect toGPS is described herein, the technology is well suited for use withnumerous other GNSS signal(s) including, but not limited to, GPSsignal(s), Glonass signal(s), Galileo signal(s), and Compass signal(s).

The technology is also well suited for use with regional navigationsatellite system signal(s) including, but not limited to, Omnistarsignal(s), StarFire signal(s), Centerpoint signal(s), Beidou signal(s),Doppler orbitography and radio-positioning integrated by satellite(DORIS) signal(s), Indian regional navigational satellite system (IRNSS)signal(s), quasi-zenith satellite system (QZSS) signal(s), and the like.

Moreover, the technology may utilize various satellite basedaugmentation system (SBAS) signal(s) such as, but not limited to, widearea augmentation system (WAAS) signal(s), European geostationarynavigation overlay service (EGNOS) signal(s), multi-functional satelliteaugmentation system (MSAS) signal(s), GPS aided geo augmented navigation(GAGAN) signal(s), and the like.

In addition, the technology may further utilize ground basedaugmentation systems (GBAS) signal(s) such as, but not limited to, localarea augmentation system (LAAS) signal(s), ground-based regionalaugmentation system (GRAS) signals, Differential GPS (DGPS) signal(s),continuously operating reference stations (CORS) signal(s), and thelike.

Although the example herein utilizes GPS, the present technology mayutilize any of the plurality of different navigation system signal(s).Moreover, the present technology may utilize two or more different typesof navigation system signal(s) to generate location information. Thus,although a GPS operational example is provided herein it is merely forpurposes of clarity.

In one embodiment, the present technology may be utilized by GNSSreceivers which access the L1 signals alone, or in combination with theL2 signal(s). A more detailed discussion of the function of a receiversuch as GPS receiver 680 can be found in U.S. Pat. No. 5,621,426. U.S.Pat. No. 5,621,426, by Gary R. Lennen, entitled “Optimized processing ofsignals for enhanced cross-correlation in a satellite positioning systemreceiver,” incorporated by reference which includes a GPS receiver verysimilar to GPS receiver 680 of FIG. 6.

In FIG. 6, received L1 and L2 signal is generated by at least one GPSsatellite. Each GPS satellite generates different signal L1 and L2signals and they are processed by different digital channel processors652 which operate in the same way as one another. FIG. 6 shows GPSsignals (L1=1575.42 MHz, L2=1227.60 MHz) entering GPS receiver 680through a dual frequency antenna 601. Antenna 601 may be a magneticallymountable model commercially available from Trimble® Navigation ofSunnyvale, Calif., 94085. Master oscillator 648 provides the referenceoscillator which drives all other clocks in the system. Frequencysynthesizer 638 takes the output of master oscillator 648 and generatesimportant clock and local oscillator frequencies used throughout thesystem. For example, in one embodiment frequency synthesizer 638generates several timing signals such as a 1st LO1 (local oscillator)signal 1400 MHz, a 2nd LO2 signal 175 MHz, a (sampling clock) SCLKsignal 25 MHz, and a MSEC (millisecond) signal used by the system as ameasurement of local reference time.

A filter/LNA (Low Noise Amplifier) 634 performs filtering and low noiseamplification of both L1 and L2 signals. The noise figure of GPSreceiver 680 is dictated by the performance of the filter/LNAcombination. The downconverter 636 mixes both L1 and L2 signals infrequency down to approximately 175 MHz and outputs the analogue L1 andL2 signals into an IF (intermediate frequency) processor 30. IFprocessor 650 takes the analog L1 and L2 signals at approximately 175MHz and converts them into digitally sampled L1 and L2 inphase (L1 I andL2 I) and quadrature signals (L1 Q and L2 Q) at carrier frequencies 420KHz for L1 and at 2.6 MHz for L2 signals respectively.

At least one digital channel processor 652 inputs the digitally sampledL1 and L2 inphase and quadrature signals. All digital channel processors652 are typically identical by design and typically operate on identicalinput samples. Each digital channel processor 652 is designed todigitally track the L1 and L2 signals produced by one satellite bytracking code and carrier signals and to form code and carrier phasemeasurements in conjunction with the microprocessor system 654. Onedigital channel processor 652 is capable of tracking one satellite inboth L1 and L2 channels.

Microprocessor system 654 is a general purpose computing device whichfacilitates tracking and measurements processes, providing pseudorangeand carrier phase measurements for a navigation processor 658. In oneembodiment, microprocessor system 654 provides signals to control theoperation of one or more digital channel processors 652. Navigationprocessor 658 performs the higher level function of combiningmeasurements in such a way as to produce position, velocity and timeinformation for the differential and surveying functions. Storage 660 iscoupled with navigation processor 658 and microprocessor system 654. Itis appreciated that storage 660 may comprise a volatile or non-volatilestorage such as a RAM or ROM, or some other computer readable memorydevice or media.

One example of a GPS chipset upon which embodiments of the presenttechnology may be implemented is the Maxwell™ chipset which iscommercially available from Trimble® Navigation of Sunnyvale, Calif.,94085.

Differential GPS

Embodiments of the present invention can use Differential GPS todetermine position information with respect to a jib of the tower crane.Differential GPS (DGPS) utilizes a reference station which is located ata surveyed position to gather data and deduce corrections for thevarious error contributions which reduce the precision of determining aposition fix. For example, as the GNSS signals pass through theionosphere and troposphere, propagation delays may occur. Other factorswhich may reduce the precision of determining a position fix may includesatellite clock errors, GNSS receiver clock errors, and satelliteposition errors (ephemeredes).

The reference station receives essentially the same GNSS signals asrovers which may also be operating in the area. However, instead ofusing the timing signals from the GNSS satellites to calculate itsposition, it uses its known position to calculate timing. In otherwords, the reference station determines what the timing signals from theGNSS satellites should be in order to calculate the position at whichthe reference station is known to be. The difference between thereceived GNSS signals and what they optimally should be is used as anerror correction factor for other GNSS receivers in the area. Typically,the reference station broadcasts the error correction to, for example, arover which uses this data to determine its position more precisely.Alternatively, the error corrections may be stored for later retrievaland correction via post-processing techniques.

Real Time Kinematic System

An improvement to DGPS methods is referred to as Real-time Kinematic(RTK). As in the DGPS method, the RTK method, utilizes a referencestation located at determined or surveyed point. The reference stationcollects data from the same set of satellites in view by the rovers inthe area. Measurements of GNSS signal errors taken at the referencestation (e.g., dual-frequency code and carrier phase signal errors) andbroadcast to one or more rovers working in the area. The rover(s)combine the reference station data with locally collected positionmeasurements to estimate local carrier-phase ambiguities, thus allowinga more precise determination of the rover's position. The RTK method isdifferent from DGPS methods in that the vector from a reference stationto a rover is determined (e.g., using the double differences method). InDGPS methods, reference stations are used to calculate the changesneeded in each pseudorange for a given satellite in view of thereference station, and the rover, to correct for the various errorcontributions. Thus, DGPS systems broadcast pseudorange correctionnumbers second-by-second for each satellite in view, or store the datafor later retrieval as described above.

RTK allows surveyors to determine a true surveyed data point in realtime, while taking the data. However, the range of useful correctionswith a single reference station is typically limited to about 70 kmbecause the variable in propagation delay (increase in apparent pathlength from satellite to rover receiver, or pseudo range) changessignificantly for separation distances beyond 70 km. This is because theionosphere is typically not homogeneous in its density of electrons, andbecause the electron density may change based on, for example, the sun'sposition and therefore time of day. Thus for surveying or otherpositioning systems which must work over larger regions, the surveyormust either place additional base stations in the regions of interest,or move his base stations from place to place. This range limitation hasled to the development of more complex enhancements that have supersededthe normal RTK operations described above, and in some cases eliminatedthe need for a base station GNSS receiver altogether. This enhancementis referred to as the “Network RTK” or “Virtual Reference Station” (VRS)system and method.

Network RTK

Network RTK typically uses three or more GNSS reference stations tocollect GNSS data and extract information about the atmospheric andsatellite ephemeris errors affecting signals within the network coverageregion. Data from all the various reference stations is transmitted to acentral processing facility, or control center for Network RTK. Suitablesoftware at the control center processes the reference station data toinfer how atmospheric and/or satellite ephemeris errors vary over theregion covered by the network. The control center computer processorthen applies a process which interpolates the atmospheric and/orsatellite ephemeris errors at any given point within the networkcoverage area and generates a pseudo range correction comprising theactual pseudo ranges that can be used to create a virtual referencestation. The control center then performs a series of calculations andcreates a set of correction models that provide the rover with the meansto estimate the ionospheric path delay from each satellite in view fromthe rover, and to take account other error contributions for those samesatellites at the current instant in time for the rover's location.

The rover is configured to couple a data-capable cellular telephone toits internal signal processing system. The surveyor operating the roverdetermines that he needs to activate the VRS process and initiates acall to the control center to make a connection with the processingcomputer. The rover sends its approximate position, based on raw GNSSdata from the satellites in view without any corrections, to the controlcenter. Typically, this approximate position is accurate toapproximately 4-7 meters. The surveyor then requests a set of “modeledobservables” for the specific location of the rover. The control centerperforms a series of calculations and creates a set of correction modelsthat provide the rover with the means to estimate the ionospheric pathdelay from each satellite in view from the rover, and to take intoaccount other error contributions for those same satellites at thecurrent instant in time for the rover's location. In other words, thecorrections for a specific rover at a specific location are determinedon command by the central processor at the control center and acorrected data stream is sent from the control center to the rover.Alternatively, the control center may instead send atmospheric andephemeris corrections to the rover which then uses that information todetermine its position more precisely.

These corrections are now sufficiently precise that the high performanceposition accuracy standard of 2-3 cm may be determined, in real time,for any arbitrary rover position. Thus the GNSS rover's raw GNSS datafix can be corrected to a degree that makes it behave as if it were asurveyed reference location; hence the terminology “virtual referencestation.” An example of a network RTK system in accordance withembodiments of the present invention is described in U.S. Pat. No.5,899,957, entitled “Carrier Phase Differential GPS CorrectionsNetwork,” by Peter Loomis, assigned to the assignee of the presentpatent application and incorporated as reference herein in its entirety.

The Virtual Reference Station method extends the allowable distance fromany reference station to the rovers. Reference stations may now belocated hundreds of miles apart, and corrections can be generated forany point within an area surrounded by reference stations.

Although the subject matter is described in a language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

We claim:
 1. A radio frequency identification (RFID) tower crane loadlocator and sway indicator comprising: a plurality of RFID tags atdifferent locations on or around the tower crane; at least two RFIDreaders at different locations on the tower crane, the RFID readerscomprising: a range determiner to provide range measurements betweeneach of the RFID readers and each of the plurality of RFID tags; a swaydeterminer coupled with a hook block of the tower crane, the swaydeterminer to provide sway information with respect to the load; anavigation satellite system (NSS) position receiver coupled with thetower crane, the NSS position receiver to determine position informationwith respect to a jib of the tower crane, wherein the NSS positionreceiver is fixedly coupled with a counterweight of the tower crane; anda load information interface to combine the information from the rangemeasurements, the sway determiner and the NSS position receiver togenerate location and sway information of the load with respect to thetower crane and provide the location and sway information in a useraccessible format.
 2. The RFID tower crane load locator and swayindicator of claim 1 wherein a first RFID reader and at least a first ofthe plurality of RFID tags is located at a trolley of the tower crane; asecond RFID reader and at least a second of the plurality of RFID tagsis located at a cab of the tower crane; and at least a third of theplurality of RFID tags is located at the hook block of the tower crane.3. The RFID tower crane load locator and sway indicator of claim 1wherein a first RFID reader and at least a first of the plurality ofRFID tags is located at a trolley of the tower crane; a second RFIDreader and at least a second of the plurality of RFID tags is located atthe hook block of the tower crane; and at least a third of the pluralityof RFID tags is located at a cab of the tower crane.
 4. The RFID towercrane load locator and sway indicator of claim 1 wherein a first RFIDreader and at least a first of the plurality of RFID tags is located atthe hook block of the tower crane; a second RFID reader and at least asecond of the plurality of RFID tags is located at a cab of the towercrane; and at least a third of the plurality of RFID tags is located ata trolley of the tower crane.
 5. The RFID tower crane load locator andsway indicator of claim 1 further comprising: a jib direction determinerto determine a direction that a jib of the tower crane is facing; andwherein the load information interface combines the range measurements,the sway determiner, the NSS position receiver and the jib directiondeterminer to generate location and sway information of the load.
 6. TheRFID tower crane load locator and sway indicator of claim 1 wherein theNSS position receiver further comprises: a first antenna fixedly coupledwith a counterweight of the tower crane; and a second antenna fixedlycoupled with approximately the front of a jib of the tower crane.
 7. TheRFID tower crane load locator and sway indicator of claim 1 furthercomprising: a second NSS position receiver fixedly coupled withapproximately the front of a jib of the tower crane.
 8. The RFID towercrane load locator and sway indicator of claim 1 wherein the positioninformation from the NSS position receiver is obtained from the positionsignal(s) group consisting of: global navigation satellite system (GNSS)signal(s), regional navigation satellite system signal(s), satellitebased augmentation system (SBAS) signal(s), and ground basedaugmentation systems (GBAS) signal(s).
 9. A radio frequencyidentification (RFID) tower crane load locator and sway indicatorcomprising: a plurality of RFID tags at different locations on or aroundthe tower crane; at least two RFID readers fixedly coupled at differentlocations on the tower crane and a handheld RFID reader at a locationnot on the tower crane, the RFID readers comprising: a range determinerto provide range measurements between the RFID readers and each of theplurality of RFID tags; a navigation satellite system (NSS) positionreceiver coupled with the tower crane, the NSS position receiver todetermine position information with respect to a jib of the tower crane,wherein the NSS position receiver is fixedly coupled with approximatelythe front of a jib of the tower crane; and a load information interfaceto combine the information from the range measurements and the NSSposition receiver to generate location and sway information of the loadwith respect to the tower crane and provide the location and swayinformation in a user accessible format.
 10. The RFID tower crane loadlocator and sway indicator of claim 9 further comprising: a swaydeterminer coupled with a hook block of the tower crane, the swaydeterminer to provide sway information with respect to the load.
 11. TheRFID tower crane load locator and sway indicator of claim 9 wherein afirst RFID reader and at least a first of the plurality of RFID tags islocated at a trolley of the tower crane; a second RFID reader and atleast a second of the plurality of RFID tags is located at a cab of thetower crane; and at least a third of the plurality of RFID tags islocated at the hook block of the tower crane.
 12. The RFID tower craneload locator and sway indicator of claim 9 wherein a first RFID readerand at least a first of the plurality of RFID tags is located at atrolley of the tower crane; a second RFID reader and at least a secondof the plurality of RFID tags is located at the hook block of the towercrane; and at least a third of the plurality of RFID tags is located ata cab of the tower crane.
 13. The RFID tower crane load locator and swayindicator of claim 9 wherein a first RFID reader and at least a first ofthe plurality of RFID tags is located at the hook block of the towercrane; a second RFID reader and at least a second of the plurality ofRFID tags is located at a cab of the tower crane; and at least a thirdof the plurality of RFID tags is located at a trolley of the towercrane.
 14. The RFID tower crane load locator and sway indicator of claim9 further comprising: a jib direction determiner to determine adirection that a jib of the tower crane is facing; wherein the loadinformation interface combines the range measurements, the swaydeterminer, the NSS position receiver and the jib direction determinerto generate location and sway information of the load.
 15. The RFIDtower crane load locator and sway indicator of claim 9 wherein the NSSposition receiver further comprises: a first antenna fixedly coupledwith a counterweight of the tower crane; and a second antenna fixedlycoupled with approximately the front of a jib of the tower crane. 16.The RFID tower crane load locator and sway indicator of claim 9 furthercomprising: a second NSS position receiver fixedly coupled with acounterweight of the tower crane.
 17. The RFID tower crane load locatorand sway indicator of claim 9 wherein the position information from theNSS position receiver is obtained from the position signal(s) groupconsisting of: global navigation satellite system (GNSS) signal(s),regional navigation satellite system signal(s), satellite basedaugmentation system (SBAS) signal(s), and ground based augmentationsystems (GBAS) signal(s).
 18. The RFID tower crane load locator and swayindicator of claim 17 wherein the GNSS signal(s) are selected from thegroup consisting of: GPS signal(s), Glonass signal(s), Galileosignal(s), and Compass signal(s).
 19. The RFID tower crane load locatorand sway indicator of claim 17 wherein the regional navigation satellitesystem signal(s) are selected from the group consisting of: Omnistarsignal(s), StarFire signal(s), Centerpoint signal(s), Beidou signal(s),Doppler orbitography and radio-positioning integrated by satellite(DORIS) signal(s), Indian regional navigational satellite system (IRNSS)signal(s), and quasi-zenith satellite system (QZSS) signal(s).
 20. TheRFID tower crane load locator and sway indicator of claim 17 wherein theSBAS signal(s) are selected from the group consisting of: wide areaaugmentation system (WAAS) signal(s), European geostationary navigationoverlay service (EGNOS) signal(s), multi-functional satelliteaugmentation system (MSAS) signal(s), and GPS aided geo augmentednavigation (GAGAN) signal(s).
 21. The RFID tower crane load locator andsway indicator of claim 17 wherein the GBAS signal(s) are selected fromthe group consisting of: local area augmentation system (LAAS)signal(s), ground-based regional augmentation system (GRAS) signals,Differential GPS (DGPS) signal(s), and continuously operating referencestations (CORS) signal(s).